diff --git a/internal/config/config_test.go b/internal/config/config_test.go
index 2bc72cb..906d823 100755
--- a/internal/config/config_test.go
+++ b/internal/config/config_test.go
@@ -133,7 +133,9 @@ func TestBindFlags(t *testing.T) {
 	flags.Int("line-width", 6, "")
 	flags.String("prompt", "watchr> ", "")
 	flags.String("refresh", "0", "")
+	flags.Bool("refresh-from-start", false, "")
 	flags.Bool("no-line-numbers", false, "")
+	flags.Bool("interactive", false, "")
 
 	// Parse with custom values
 	err := flags.Parse([]string{"--shell=bash", "--preview-size=50%", "--line-width=8"})
@@ -239,7 +241,9 @@ preview-size: "60%"
 	flags.Int("line-width", 6, "")
 	flags.String("prompt", "watchr> ", "")
 	flags.String("refresh", "0", "")
+	flags.Bool("refresh-from-start", false, "")
 	flags.Bool("no-line-numbers", false, "")
+	flags.Bool("interactive", false, "")
 
 	// Override shell via flag
 	err := flags.Parse([]string{"--shell=bash"})
@@ -556,6 +560,107 @@ func TestGetDuration(t *testing.T) {
 	}
 }
 
+func TestRefreshFromStartDefault(t *testing.T) {
+	_, cleanup := isolateConfig(t)
+	defer cleanup()
+
+	Init()
+
+	// Default should be false
+	if got := GetBool(KeyRefreshFromStart); got != false {
+		t.Errorf("expected default refresh-from-start false, got %v", got)
+	}
+}
+
+func TestRefreshFromStartFromConfigFile(t *testing.T) {
+	tmpDir, cleanup := isolateConfig(t)
+	defer cleanup()
+
+	// Create config file with refresh-from-start: true
+	configPath := filepath.Join(tmpDir, "watchr.yaml")
+	configContent := `refresh-from-start: true
+`
+	if err := os.WriteFile(configPath, []byte(configContent), 0644); err != nil {
+		t.Fatalf("failed to write config file: %v", err)
+	}
+
+	Init()
+
+	if got := GetBool(KeyRefreshFromStart); got != true {
+		t.Errorf("expected refresh-from-start true from config file, got %v", got)
+	}
+}
+
+func TestRefreshFromStartFromFlag(t *testing.T) {
+	_, cleanup := isolateConfig(t)
+	defer cleanup()
+
+	Init()
+
+	// Create flags and parse
+	flags := pflag.NewFlagSet("test", pflag.ContinueOnError)
+	flags.String("shell", "sh", "")
+	flags.String("preview-size", "40%", "")
+	flags.String("preview-position", "bottom", "")
+	flags.Int("line-width", 6, "")
+	flags.String("prompt", "watchr> ", "")
+	flags.String("refresh", "0", "")
+	flags.Bool("refresh-from-start", false, "")
+	flags.Bool("no-line-numbers", false, "")
+	flags.Bool("interactive", false, "")
+
+	// Parse with refresh-from-start=true
+	err := flags.Parse([]string{"--refresh-from-start=true"})
+	if err != nil {
+		t.Fatalf("failed to parse flags: %v", err)
+	}
+
+	BindFlags(flags)
+
+	if got := GetBool(KeyRefreshFromStart); got != true {
+		t.Errorf("expected refresh-from-start true from flag, got %v", got)
+	}
+}
+
+func TestRefreshFromStartFlagOverridesConfig(t *testing.T) {
+	tmpDir, cleanup := isolateConfig(t)
+	defer cleanup()
+
+	// Create config file with refresh-from-start: true
+	configPath := filepath.Join(tmpDir, "watchr.yaml")
+	configContent := `refresh-from-start: true
+`
+	if err := os.WriteFile(configPath, []byte(configContent), 0644); err != nil {
+		t.Fatalf("failed to write config file: %v", err)
+	}
+
+	Init()
+
+	// Create flags and parse with refresh-from-start=false
+	flags := pflag.NewFlagSet("test", pflag.ContinueOnError)
+	flags.String("shell", "sh", "")
+	flags.String("preview-size", "40%", "")
+	flags.String("preview-position", "bottom", "")
+	flags.Int("line-width", 6, "")
+	flags.String("prompt", "watchr> ", "")
+	flags.String("refresh", "0", "")
+	flags.Bool("refresh-from-start", false, "")
+	flags.Bool("no-line-numbers", false, "")
+	flags.Bool("interactive", false, "")
+
+	err := flags.Parse([]string{"--refresh-from-start=false"})
+	if err != nil {
+		t.Fatalf("failed to parse flags: %v", err)
+	}
+
+	BindFlags(flags)
+
+	// Flag should override config
+	if got := GetBool(KeyRefreshFromStart); got != false {
+		t.Errorf("expected refresh-from-start false (flag override), got %v", got)
+	}
+}
+
 func TestRefreshDurationFromConfigFile(t *testing.T) {
 	tmpDir, cleanup := isolateConfig(t)
 	defer cleanup()
diff --git a/internal/runner/runner_test.go b/internal/runner/runner_test.go
index c1292e3..e4e0526 100755
--- a/internal/runner/runner_test.go
+++ b/internal/runner/runner_test.go
@@ -378,3 +378,147 @@ func TestSanitizeLine(t *testing.T) {
 		})
 	}
 }
+
+func TestRunStreaming(t *testing.T) {
+	r := NewRunner("sh", "echo 'line1'; echo 'line2'; echo 'line3'")
+	ctx := context.Background()
+
+	result := r.RunStreaming(ctx, nil)
+
+	// Wait for completion
+	for !result.IsDone() {
+		time.Sleep(10 * time.Millisecond)
+	}
+
+	lines := result.GetLines()
+	if len(lines) != 3 {
+		t.Fatalf("expected 3 lines, got %d", len(lines))
+	}
+
+	if lines[0].Content != "line1" {
+		t.Errorf("expected first line 'line1', got %q", lines[0].Content)
+	}
+
+	if result.GetCurrentLineCount() != 3 {
+		t.Errorf("expected CurrentLineCount 3, got %d", result.GetCurrentLineCount())
+	}
+}
+
+func TestRunStreamingWithPreviousLines(t *testing.T) {
+	// Previous lines that should be overwritten
+	prevLines := []Line{
+		{Number: 1, Content: "old1"},
+		{Number: 2, Content: "old2"},
+		{Number: 3, Content: "old3"},
+		{Number: 4, Content: "old4"},
+		{Number: 5, Content: "old5"},
+	}
+
+	r := NewRunner("sh", "echo 'new1'; echo 'new2'; echo 'new3'")
+	ctx := context.Background()
+
+	result := r.RunStreaming(ctx, prevLines)
+
+	// Verify PrevLineCount is set
+	if result.PrevLineCount != 5 {
+		t.Errorf("expected PrevLineCount 5, got %d", result.PrevLineCount)
+	}
+
+	// Wait for completion
+	for !result.IsDone() {
+		time.Sleep(10 * time.Millisecond)
+	}
+
+	lines := result.GetLines()
+
+	// Should still have 5 lines (3 new + 2 old remaining)
+	if len(lines) != 5 {
+		t.Fatalf("expected 5 lines (in-place update), got %d", len(lines))
+	}
+
+	// First 3 lines should be overwritten
+	if lines[0].Content != "new1" {
+		t.Errorf("expected line 0 'new1', got %q", lines[0].Content)
+	}
+	if lines[1].Content != "new2" {
+		t.Errorf("expected line 1 'new2', got %q", lines[1].Content)
+	}
+	if lines[2].Content != "new3" {
+		t.Errorf("expected line 2 'new3', got %q", lines[2].Content)
+	}
+
+	// Remaining lines should be old (not touched)
+	if lines[3].Content != "old4" {
+		t.Errorf("expected line 3 'old4', got %q", lines[3].Content)
+	}
+	if lines[4].Content != "old5" {
+		t.Errorf("expected line 4 'old5', got %q", lines[4].Content)
+	}
+
+	// CurrentLineCount should be 3 (only new lines written)
+	if result.GetCurrentLineCount() != 3 {
+		t.Errorf("expected CurrentLineCount 3, got %d", result.GetCurrentLineCount())
+	}
+}
+
+func TestRunStreamingMoreLinesThanPrevious(t *testing.T) {
+	// Previous lines (fewer than new output)
+	prevLines := []Line{
+		{Number: 1, Content: "old1"},
+		{Number: 2, Content: "old2"},
+	}
+
+	r := NewRunner("sh", "echo 'new1'; echo 'new2'; echo 'new3'; echo 'new4'")
+	ctx := context.Background()
+
+	result := r.RunStreaming(ctx, prevLines)
+
+	// Wait for completion
+	for !result.IsDone() {
+		time.Sleep(10 * time.Millisecond)
+	}
+
+	lines := result.GetLines()
+
+	// Should have 4 lines (2 overwritten + 2 appended)
+	if len(lines) != 4 {
+		t.Fatalf("expected 4 lines, got %d", len(lines))
+	}
+
+	// All lines should be new
+	for i, expected := range []string{"new1", "new2", "new3", "new4"} {
+		if lines[i].Content != expected {
+			t.Errorf("expected line %d %q, got %q", i, expected, lines[i].Content)
+		}
+	}
+
+	if result.GetCurrentLineCount() != 4 {
+		t.Errorf("expected CurrentLineCount 4, got %d", result.GetCurrentLineCount())
+	}
+}
+
+func TestStreamingResultThreadSafety(t *testing.T) {
+	r := NewRunner("sh", "for i in $(seq 1 100); do echo line$i; done")
+	ctx := context.Background()
+
+	result := r.RunStreaming(ctx, nil)
+
+	// Concurrently read while streaming
+	done := make(chan bool)
+	go func() {
+		for !result.IsDone() {
+			_ = result.GetLines()
+			_ = result.LineCount()
+			_ = result.GetCurrentLineCount()
+			time.Sleep(5 * time.Millisecond)
+		}
+		done <- true
+	}()
+
+	<-done
+
+	// Should complete without race conditions
+	if result.LineCount() != 100 {
+		t.Errorf("expected 100 lines, got %d", result.LineCount())
+	}
+}
diff --git a/internal/ui/ui_test.go b/internal/ui/ui_test.go
index 8180c04..cfcaa0d 100755
--- a/internal/ui/ui_test.go
+++ b/internal/ui/ui_test.go
@@ -284,3 +284,132 @@ func TestVisibleLines(t *testing.T) {
 		t.Errorf("expected %d visible lines with absolute preview size, got %d", expected, visible)
 	}
 }
+
+func TestUpdateFilteredPreservesOffset(t *testing.T) {
+	cfg := Config{
+		Command: "echo test",
+		Shell:   "sh",
+	}
+
+	m := initialModel(cfg)
+	m.height = 20 // Enough for visibleLines to return > 0
+
+	// Add many test lines
+	for i := 1; i <= 100; i++ {
+		m.lines = append(m.lines, runner.Line{Number: i, Content: "line content"})
+	}
+
+	// Set initial state with offset
+	m.filter = ""
+	m.updateFiltered()
+	m.offset = 50
+	m.cursor = 55
+
+	// Simulate streaming update - add more lines without changing filter
+	m.lines = append(m.lines, runner.Line{Number: 101, Content: "new line"})
+	m.updateFiltered()
+
+	// Offset should be preserved (or clamped if necessary)
+	if m.offset < 50 {
+		t.Errorf("expected offset to be preserved (>= 50), got %d", m.offset)
+	}
+
+	// Cursor should be preserved
+	if m.cursor != 55 {
+		t.Errorf("expected cursor to be preserved at 55, got %d", m.cursor)
+	}
+}
+
+func TestUpdateFilteredClampsOffsetWhenNeeded(t *testing.T) {
+	cfg := Config{
+		Command: "echo test",
+		Shell:   "sh",
+	}
+
+	m := initialModel(cfg)
+	m.height = 20
+
+	// Add test lines
+	for i := 1; i <= 100; i++ {
+		m.lines = append(m.lines, runner.Line{Number: i, Content: "line content"})
+	}
+
+	m.filter = ""
+	m.updateFiltered()
+	m.offset = 90
+	m.cursor = 95
+
+	// Now filter to fewer lines
+	m.filter = "xyz" // No matches
+	m.updateFiltered()
+
+	// Offset should be clamped to valid range
+	if m.offset != 0 {
+		t.Errorf("expected offset to be clamped to 0, got %d", m.offset)
+	}
+
+	// Cursor should be clamped
+	if m.cursor != 0 {
+		t.Errorf("expected cursor to be clamped to 0, got %d", m.cursor)
+	}
+}
+
+func TestConfigRefreshFromStart(t *testing.T) {
+	// Test with RefreshFromStart false (default)
+	cfg := Config{
+		Command:          "echo test",
+		Shell:            "sh",
+		RefreshInterval:  5 * time.Second,
+		RefreshFromStart: false,
+	}
+
+	if cfg.RefreshFromStart {
+		t.Error("expected RefreshFromStart to be false by default")
+	}
+
+	// Test with RefreshFromStart true
+	cfg.RefreshFromStart = true
+	if !cfg.RefreshFromStart {
+		t.Error("expected RefreshFromStart to be true after setting")
+	}
+}
+
+func TestModelUserScrolled(t *testing.T) {
+	cfg := Config{
+		Command: "echo test",
+		Shell:   "sh",
+	}
+
+	m := initialModel(cfg)
+
+	// Initially should be false
+	if m.userScrolled {
+		t.Error("expected userScrolled to be false initially")
+	}
+
+	// After setting, should be true
+	m.userScrolled = true
+	if !m.userScrolled {
+		t.Error("expected userScrolled to be true after setting")
+	}
+}
+
+func TestModelRefreshGeneration(t *testing.T) {
+	cfg := Config{
+		Command: "echo test",
+		Shell:   "sh",
+	}
+
+	m := initialModel(cfg)
+
+	// Initially should be 0
+	if m.refreshGeneration != 0 {
+		t.Errorf("expected refreshGeneration to be 0 initially, got %d", m.refreshGeneration)
+	}
+
+	// After incrementing
+	m.refreshGeneration++
+	if m.refreshGeneration != 1 {
+		t.Errorf("expected refreshGeneration to be 1 after increment, got %d", m.refreshGeneration)
+	}
+}